Objectives: The objective of this study was to determine whether site-specific cancer incidence among farmers exposed to the insecticide lindane (g-hexachlorocyclohexane) while dipping sheep differs from that of the general population in Iceland.
Methods: Cohorts of 7882 men and 429 women, who, according to records on sheep dipping, were sheep owners, were followed from 1962 to 2003 in the Cancer Registry for cancer incidence. The observed number of cancers was compared with expected values, calculated on the basis of person-years of risk and cancer incidence in the general population of Iceland.
Results: For men the standardized incidence ratio (SIR) for all cancer sites was 0.79, with a 95% confidence interval (95% CI) of 0.76-0.83. For both the men and the women a significantly increased risk for lip cancer was found, with SIR of 1.50 (95% CI 1.08-2.04) and 9.09 (95% CI 1.02-32.82), respectively. The SIR for several cancer sites were lower than unity for both the men and women. Examples were cancers of the colon, rectum, pancreas, stomach, lungs, kidney, bladder, and brain and nervous system.
Conclusions: The decreased risk of most cancers among these sheep farmers agrees with findings reported previously among farmers from other countries, as well as in Iceland. Cancer of the lip was the only cancer type in significant excess among both genders, and the stomach cancer rates were near unity, but, in previous studies on Icelandic farmers, an increase had been found for stomach cancer. The site-specific cancer incidence for sheep-dipping farmers did not differ substantially from that of the general population.